At-speed test access port operations

ABSTRACT

This disclosure describes different ways to improve the operation of a device&#39;s 1149.1 TAP to where the TAP can perform at-speed Update &amp; Capture, Shift &amp; Capture and Back to Back Capture &amp; Shift operations. In a first embodiment of the disclosure the at-speed operations are achieved by time division multiplexing CMD signals onto the TMS input to the TAP. The CMD signals are input to a CMD circuit that operates in conjunction with a Dual Port Router to execute the at-speed operations of a circuit. In a second embodiment of the disclosure the at-speed operations are achieved by detecting the TAP&#39;s Exit1DR state as a CMD signal that is input to the CMD circuit that operates in conjunction with a Dual Port Router to execute the at-speed operations of a circuit. In a third embodiment of the disclosure the at-speed operations are achieved by detecting the TAP&#39;s Exit1DR and PauseDR states and in response producing Capture and Update signals that are input to a Programmable Switch that operates in conjunction with a Dual Port Router to execute the at-speed operations of a circuit. In a fourth embodiment of the disclosure the at-speed operations are achieved by detecting the TAP&#39;s Exit1DR and PauseDR states and inputting these states to a Dual Port Router to control the at-speed operations of a circuit. Each of the embodiments may be augmented to include externally accessible Update and Capture input signals that can be selected to allow a tester to directly control the at-speed operations of a circuit. The improvements of the disclosure are achieved without requiring any additional IC pins beyond the 4 required TAP pins, except for examples showing use of additional data input pins (TDI or WPI signals), additional data output pins (TDO or WPO signals) or examples showing use of additional control input pins (Capture and Update signals). Devices including the TAP improvements can be operated compliantly in a daisy-chain arrangement with devices that don&#39;t include the TAP improvements.

This application is a divisional of prior application Ser. No.14/179,754, filed Feb. 13, 2014, currently pending;

Which was a divisional of prior application Ser. No. 13/188,078, filedJul. 21, 2011; now U.S. Pat. No. 8,694,844, issued Apr. 8, 2014;

Which claims priority from Provisional Application No. 61/368,906, filedJul. 29, 2010,

And also claims priority from Provisional Application No. 61/406,674,filed Oct. 26, 2010.

This disclosure relates generally to IEEE 1149.1 Test Access Ports andin particular to operational improvements to IEEE 1149.1 Test AccessPorts.

RELATED ART

This disclosure is related to U.S. Pat. No. 7,404,129 and pending patentapplication Ser. Nos. 12/410,561 and 13/028,575, all incorporated hereinby reference.

FIELD OF THE INVENTION Background

The IEEE 1149.1 Test Access Port (TAP) is used widely in thesemiconductor industry as an IC interface for controlling many types ofembedded IC circuits, such as but not limited to test circuits, debugcircuits, programming circuits, instrumentation circuits and tracecircuits. The TAP has proven for the last 20 years to be effective incontrolling the operations of embedded IC circuits. However, the TAP hasnot proven to be effective in controlling the operations of embedded ICcircuits that depend on at-speed Update & Capture and Shift & Captureoperations. The first part of this disclosure (FIGS. 1-7) describes theat-speed Update & Capture and Shift & Capture problem. The second partof this disclosure (FIGS. 8-41) describes novel solutions to thisproblem using various examples of implementation.

SUMMARY OF THE DISCLOSURE

This disclosure describes novel solutions to solve the TAP's at-speedUpdate & Capture and Shift & Capture problem by augmenting the TAP withadditional circuitry. In the first disclosed solution of FIGS. 8-28, theat-speed operations are achieved by time division multiplexing CMDsignals onto the TMS input to the TAP and inputting the CMD signals to acommand (CMD) circuit that controls the at-speed operations of a dataregister. In the second disclosed solution of FIGS. 29A-33, the at-speedoperations are achieved by detecting the TAP's Exit1DR state to producethe CMD signals to the CMD circuit that controls the at-speed operationsof a data register. In the third disclosed solution of FIGS. 34A-38, theat-speed operations are achieved by detecting the TAP's Exit1DR andPauseDR states to produce at-speed Update and Capture signals that areinput a data register via a Programmable Switch (PSW) circuit. In thefourth disclosed solution of FIGS. 39-41, the at-speed operations areachieved by detecting the TAP's Exit1DR and PauseDR states to produceat-speed Update and Capture signals that are input to a data registervia a Dual Port Router. All the disclosed solutions may be augmentedwith externally accessible Update and Capture signals to allow a testerto directly control the at-speed operations of a data register.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an IEEE 1149.1 TAP architecture.

FIG. 2 illustrates a Router circuit for routing Tap State Machine (TSM)data register control (DRC) signals to a data register.

FIG. 3 illustrates the state diagram of the TSM.

FIG. 4 illustrates an asynchronous CSU data register being control bythe TSM, via a router.

FIG. 5 illustrates a synchronous CSU data register being control by theTSM, via a router.

FIG. 6 illustrates an asynchronous CS data register being control by theTSM, via a router.

FIG. 7 illustrates a synchronous CS data register being control by theTSM, via a router.

FIG. 8 illustrates an IEEE 1149.1 TAP augmented with a command (CMD)circuit and Dual Port Router according to the disclosure.

FIG. 9 illustrates a Dual Port Router circuit for routing DRC signalsfrom a TSM or a CMD circuit to data registers according to thedisclosure.

FIG. 10 illustrates the timing diagram for performing CS or CSUoperations using the CMD circuit according to the disclosure.

FIG. 11 illustrates an asynchronous CSU data register being control byeither the TSM or CMD circuit, via a Dual Port Router according to thedisclosure.

FIG. 12 illustrates a synchronous CSU data register being control by theTSM or CMD circuit, via a Dual Port Router according to the disclosure.

FIG. 13 illustrates an asynchronous CS data register being control byeither the TSM or CMD circuit, via a Dual Port Router according to thedisclosure.

FIG. 14 illustrates a synchronous CS data register being control by theTSM or CMD circuit, via a Dual Port Router according to the disclosure.

FIG. 15 illustrates an asynchronous CS data register being control bythe TSM or CMD circuit, via a Dual Port Router according to thedisclosure.

FIG. 16 illustrates a first test compression architecture being controlby the TSM or CMD circuit, via a Dual Port Router according to thedisclosure.

FIG. 17 illustrates a second test compression architecture being controlby the TSM or CMD circuit, via a Dual Port Router according to thedisclosure.

FIG. 18 illustrates an IEEE 1500 wrapper architecture being control bythe TSM or CMD circuit, via a Dual Port Router according to thedisclosure.

FIG. 19 illustrates a read/write circuit architecture being control bythe TSM or CMD circuit, via a Dual Port Router according to thedisclosure.

FIG. 20 illustrates an IEEE P1687 instrumentation architecture beingcontrol by the TSM or CMD circuit, via a Dual Port Router according tothe disclosure.

FIG. 21 illustrates a first daisy-chain of devices performing anexternal test operation according to the disclosure.

FIG. 22 illustrates a second daisy-chain of devices performing aninternal test operation according to the disclosure.

FIG. 23 illustrates a JTAG/1149.1 bus controller

FIG. 24 illustrates a JTAG/1149.1 bus controlled augmented with a CMDcircuit according to the disclosure

FIG. 25 illustrates an example implementation of the JTAG Controller CMDcircuit according to the disclosure.

FIG. 26 Illustrates a CSU or CS circuit connectable to a TSM or CMDcircuit with additional Capture and Update inputs via a Dual Port Routeraccording to the disclosure.

FIG. 27 illustrates a CMD circuit with a Capture input according to thedisclosure.

FIG. 28 illustrates a CMD circuit with Capture and Update inputsaccording to the disclosure.

FIG. 29A illustrates an IEEE 1149.1 TAP augmented with a CMD circuitthat receives CMD signal from the TSM according to the disclosure.

FIG. 29B illustrates gating circuitry for outputting a CMD signal to theCMD circuit when the TSM is in the Exit1DR state according to thedisclosure.

FIG. 30 illustrates a timing diagram of the TSM outputting CMD signalsto the CMD circuit to perform CSOP, CSUOP and B2BCSOP operationsaccording to the disclosure.

FIG. 31 illustrates a data register being controlled by a CMD circuitthat receives CMD signals for the TSM according to the disclosure.

FIG. 32 illustrates a circuit for producing clock signals on the TSM'sClockDR output during certain TSM states according to the disclosure.

FIG. 33 Illustrates a CSU or CS circuit connectable to a TSM or CMDcircuit with additional Capture and Update inputs via a Dual Port Routeraccording to the disclosure.

FIG. 34A illustrates an IEEE 1149.1 TAP augmented with a programmableswitch (PSW) circuit that receives control signals from the TSMaccording to the disclosure.

FIG. 34B illustrates gating circuitry for outputting control signals tothe PSW when the TSM is in the Exit1DR or PauseDR states according tothe disclosure according to the disclosure.

FIG. 35 illustrates a timing diagram of the TSM outputting controlsignals to the PSW circuit to perform CSOP, CSUOP and B2BCSOP operationsaccording to the disclosure.

FIG. 36 illustrates a data register being controlled by a PSW thatreceives control signals from the TSM according to the disclosure.

FIG. 37 Illustrates a CSU or CS circuit connectable to a TSM or PSWcircuit with additional Capture and Update inputs via a Dual Port Routeraccording to the disclosure.

FIG. 38 illustrates a PSW circuit with Capture and Update inputsaccording to the disclosure.

FIG. 39 illustrates an IEEE 1149.1 TAP augmented with TSM Exit1DR andPauseDR state detection circuitry and a Dual Port Router according tothe disclosure.

FIG. 40 illustrates an IEEE 1149.1 TAP augmented with TSM Exit1DR andPauseDR state detection circuitry, a multiplexer and a Dual Port Routeraccording to the disclosure.

FIG. 41 Illustrates a CSU or CS circuit connectable to a DRC multiplexervia a Dual Port Router according to the disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates a prior art example TAP architecture 100 consistingof a TAP state machine (TSM) 102, an instruction register 104, dataregisters 106, a Data Register Control (DRC) signal Router 108 and TDOmultiplexer 110. The TSM operates through states shown in FIG. 3 to; (1)place the TAP in a Test Logic Reset state, (2) place the TAP in a RunTest/Idle state, (3) perform an instruction register scan operation or(4) perform a data register scan operation. The instruction registeroutputs Data Register Enable (DRE) signals that select the TSM's DRCsignals to pass through the Router to a data register to be accessed.

FIG. 2 illustrates the Router 108 which consists of routing circuits 202that connect the TSM's DRC outputs to the DRC inputs of a data register106. Once connected the data register can be accessed from TDI to TDO bytransitioning the TAP state machine through its SelectDR, CaptureDR,ShiftDR, Exit1DR and UpdateDR states, as shown in the TAP's TSM statediagram of FIG. 3.

FIG. 4 illustrates an asynchronous Capture, Shift and Update (CSU) dataregister 402 connected to the TSM 102 via a routing circuit 108. Therouting circuit 108 in this and other following routing circuitexamples, consists of gating circuits that allow the TSM to control thedata register 402 when it has been selected for access by DREinstruction inputs. Asynchronous means the data register is timed by theTSM's gated ClockDR output. CSU type data registers, such as IEEE 1149.1boundary scan registers, are well known. In response to DRE input, thegating circuits of the router circuit connect the TSM's ClockDR, ShiftDRand UpdateDR outputs, all known in the art, to the data registersClockDR, ShiftDR and UpdateDR inputs. Once connected, the TSMtransitions through its SelectDR, CaptureDR, ShiftDR, Exit1DR andUpdateDR states of FIG. 3 to operate the data register. When the dataregister is not being accessed by the TSM, the gating circuits ofrouting circuit 108 are set by DRE inputs to place the data register'sClockDR, ShiftDR and UpdateDR inputs to inactive states.

FIG. 5 illustrates a synchronous CSU data register 502 connected to theTSM 102 via a routing circuit 108. Synchronous means the data registeris timed by the TCK signal. Synchronous operation requires the dataregister's scan cells to provide a holding state such that when the dataregister is not performing a Capture, Shift or Update operation itmaintains it's current state. The Capture signal indicates the TSM is inthe CaptureDR state of FIG. 3, the Shift signal indicates the TSM is inthe ShiftDR state of FIG. 3, the Update signal indicates the TSM is inthe UpdateDR state of FIG. 3. In response to DRE input, the routingcircuit connects the TSM's Capture, Shift and Update state outputs tothe data registers Capture, Shift and Update inputs. Once connected theTSM transitions through its SelectDR, CaptureDR, ShiftDR, Exit1DR andUpdateDR states of FIG. 3 to operate the data register. When the dataregister is not being accessed by the TSM, the gating circuits ofrouting circuit 108 are set by DRE inputs to place the data register'sCapture, Shift and Update inputs to inactive states.

FIG. 6 illustrates an asynchronous Capture and Shift (CS) data register602 connected to the TSM 102 via a routing circuit 108. CS type dataregisters, such as internal scan path registers are well known. Inresponse to DRE input, the routing circuit connects the TSM's ClockDRand ShiftDR outputs to the data registers ClockDR and ShiftDR inputs.Once connected, the TSM transitions through its SelectDR, CaptureDR,ShiftDR, Exit1DR and UpdateDR states of FIG. 3 to operate the dataregister. When the data register is not being accessed by the TSM, thegating circuits of routing circuit 108 are set by DRE inputs to placethe data register's ClockDR and ShiftDR inputs to inactive states.

FIG. 7 illustrates a synchronous CS data register 702 connected to theTSM 102 via a routing circuit 108. In response to DRE input, the routingcircuit connects the TSM's Capture and Shift state outputs to the dataregisters Capture and Shift inputs. Once connected, the TSM transitionsthrough its SelectDR, CaptureDR, ShiftDR, Exit1DR and UpdateDR states ofFIG. 3 to operate the data register. When the data register is not beingaccessed by the TSM, the gating circuits of routing circuit 108 are setby DRE inputs to place the data register's Capture and Shift inputs toinactive states.

The TSM state transitions of the CSU scan cycles of FIGS. 4 and 5illustrate the problematic dead states SelectDR and Exit1DR in dottedline boxes. When an Update operation occurs in the UpdateDR state ittakes 2 and one half TCKs before a capture operation occurs in theCaptureDR state. This prevents at-speed Update & Capture scanoperations. The TSM state transitions of the CS scan cycles of FIGS. 6and 7 illustrate the problematic dead states SelectDR, Exit1DR andUpdateDR in dotted line boxes. When the last shift operation occurs inthe ShiftDR state it takes 4 TCKs before a capture operation occurs inthe CaptureDR state. This prevents at-speed Shift & Capture scanoperations.

The dead states of FIGS. 4-7, that prevent at-speed CSU and CS scanoperations, are well known in the industry. Many solutions have beenproposed to address this problem. Some of the early solutions aredescribed and referenced below.

Solution 1—Chapter 18 of IEEE Computer Society Press “The Test AccessPort and Boundary Scan Architecture” 1990, by Maunder. This solutiondefined a ScanTest instruction that can be loaded into the TAPinstruction register that “reprograms” the TSM state assignments towhere at-speed capture operations can occur after the last shiftoperation. This solution eliminates the dead states in CS scanoperations but does not eliminate the dead states in CSU scanoperations. Also the solution only applies to standalone device testing,i.e. it cannot be used when the device is daisy-chained with otherdevices.

Solution 2—Paper “Built-In-Test Using Boundary Scan”, ATE &Instrumentation Conference, 1989, pg 15-22 by Whetsel. This solutiondefined BIST and DelayTest instructions that can be loaded into the TAPinstruction register and executed in the Run Test/Idle state to performat-speed update and capture operations. This solution does not addressthe dead state problem in CSU and CS scan operations.

Solution 3—Paper “Early Capture for Boundary Scan Timing Measurements,IEEE International Test Conference”, 1996 by Lofstrom. This solutiondefined an EarlyCapture instruction that can be loaded into the TAPinstruction register to allow the TMS signal to be used as a captureclock that can be applied after an update operation. This solutionprovides an at-speed update and capture operation, but it does noteliminate the need to traverse the dead states. It also only works withCSU scan operations, not CS scan operations.

Solution 4—IEEE Standard 1149.6, “A Standard for Boundary Scan Testingof Advanced Digital Networks”. This solution was based on a new standard(IEEE 1149.6) that defines new instructions (ExtestPulse & ExtestTrain)that allow at-speed update and capture operations to be executed in theRun Test/Idle state. Like solution 2, this solution does not address thedead state problem in CSU and CS scan operations.

First Disclosed Solution—FIGS. 8-33

The first solution described in this disclosure to eliminate theproblematic dead states of FIGS. 4-7 involves augmenting the TAP 100with a Command circuit and a Dual Port Router. The Command circuit andDual Port Router can operate while the TSM 102 is in the ShiftDR stateof FIG. 3 to perform at-speed Update and Capture operations on CSU dataregisters and at-speed Shift and Capture operations on CS dataregisters.

FIG. 8 illustrates a TAP 800 that has been augmented with a Command(CMD) circuit 802 and a Dual Port Router 804, otherwise TAP 800 is thesame as TAP 100 of FIG. 1. The CMD circuit 802 has inputs connected tothe TCK, TMS, DRE and DRC outputs. One port of the Dual Port Router 804is connected to the DRC outputs of the CMD circuit and the other port isconnected to the DRC outputs of the TSM. The DRE signals from theinstruction register enable or disable the CMD circuit. The DRE signalsalso control the Dual Port Router such that the Router's DRC outputs toa data register 106 may be controlled by the TSM 102 as previouslydescribed or by the CMD circuit 804.

FIG. 9 illustrates an example Dual Port Router 804 which consists ofrouting circuits 902 that, in response to the DRE inputs, connect theDRC outputs from the TSM to the DRC inputs of a selected data register106 or connect the DRC outputs of the CMD circuit to the DRC inputs of aselected data register 106. If the data register is connected to the DRCoutputs of the TSM it can be accessed for CSU or CS scan operations thatare controlled by the TSM, as previously described. If the data registeris connected to the DRC outputs of the CMD circuit it can be accessedfor CSU or CS scan operations that are controlled by the CMD circuit.

FIG. 10 illustrates the timing of performing a CSU scan operation(CSUOP) 1002 or a CS scan operation (CSOP) 1004 using the CMD circuit.When the CMD circuit is being used to access a data register, the TSMwill transition to and remain in the ShiftDR state 1006. In the ShiftDRstate, the data register shifts data from TDI to TDO. At appropriatetimes during the shifting, CMD signals 1008 are input to the CMD circuiton the falling edge of TCK via the TMS signal. Between CMD signalinputs, No Operation (NOP) signals 1010 are input to the CMD circuit onthe falling edge of TCK via TMS. During CMD controlled access to thedata register, the TSM continues to receive normal TMS inputs 1012 onthe rising edge of TCK to maintain the TSM in the ShiftDR state. At theend of a CMD circuit controlled scan operation, the TSM will receive TMSinput to transition out of the ShiftDR state to terminate the dataregister access operation.

As seen in FIG. 10, if a CSU type data register is being accessed, aCSUOP will be performed in response to a CMD signal input. The CSUOPperforms an Update operation 1014 after the last Shift (Shift N)operation, performs a Capture operation 1016 and then resumes the Shiftoperation. This Update, Capture and Shift sequence is repeated each timea CMD signal is input on TMS. Since the TSM remains in the ShiftDR statewhile the CMD circuit controls the CSU data register, there are no deadstates in the CSUOP cycles of FIG. 10.

Also as seen in FIG. 10, if a CS type data register is being accessed, aCSOP will be performed in response to a CMD signal input. The CSOPperforms a Capture operation 1018 after the last Shift (Shift N)operation then resumes the Shift operation. This Capture and Shiftsequence is repeated each time a CMD signal is input on TMS. Since theTSM remains in the ShiftDR state while the CMD circuit controls the CSdata register, there are no dead states in the CSOP cycles of FIG. 10.

FIG. 11 illustrates the asynchronous CSU data register 402 of FIG. 4connected to the TSM and a CMD circuit via an example Dual Port Router804. The DRE inputs control the Dual Port Router to allow the dataregister to be accessed by the TSM as described in FIG. 4 or by the CMDcircuit as described in FIG. 10. The CMD circuit in this example issimply two serially connected FFs that input the CMD signal from TMS onthe falling edge of TCK.

The Dual Port Router 804 in this example is simply multiplexers andgating connected as shown that are controlled by the DRE input from theinstruction register. When the data register is to be controlled by theTSM, the DRE input routes the ClockDR, ShiftDR and UpdateDR outputs fromthe TSM through the Dual Port Router to the ClockDR, ShiftDR andUpdateDR inputs of the data register. When the data register is to becontrolled by the CMD circuit, the DRE input routes the Capture (C) andUpdate (U) signals from the CMD circuit and the ClockDR signal from theTSM through the Dual Port Router to the ClockDR, ShiftDR and UpdateDRinputs of the data register. The ClockDR output from the TSM will berunning since the TSM will be in the ShiftDR state. The first port ofthis example Dual Port Router is defined as being the ClockDR, ShiftDRand UpdateDR inputs from the TSM. The second port of this example DualPort Router is defined as being the Capture (C) and Update (U) inputsfrom the CMD circuit and the ClockDR input from the TSM.

During access by the CMD circuit, the first FF inputs the CMD signalfrom TMS and outputs the Update (U) signal to the Dual Port Router whichoutputs the UpdateDR signal to the data register to cause the dataregister to perform an Update operation. The Update (U) signal from theCMD circuit is gated with the ClockDR signal from the TSM to produce anupdate clock pulse on the UpdateDR input to the data register on therising edge of TCK. The CMD signal is then shifted into the second FFwhich outputs a Capture (C) signal to the Dual Port Router which outputsa logic level on the ShiftDR signal to the data register to cause thedata register to perform a Capture operation on the next rising edge ofClockDR, which is driven by TCK. The Update (U) and Capture (C) signalsare stable during the rising edge ClockDR operations since they areregistered in the FFs on the falling edge of TCK. The Update and Captureoperation sequence is repeated each time a CMD signal is input to theCMD circuit. While this example Dual Port Router produces the updateclock pulse on the rising edge of ClockDR another example Dual PortRouter could produce the update clock pulse on the falling edge ofClockDR if desired.

While not shown in FIG. 11, the FFs of the CMD circuit of this and otherfollowing CMD circuit examples will be initialized by the DRE input atthe beginning of a data register test access operation, as shown in FIG.9, such that the Update (U) and Capture (C) outputs are not asserteduntil a CMD signal is received.

FIG. 12 illustrates the synchronous CSU data register 502 of FIG. 5connected to the TSM 102 and the CMD circuit 802 of FIG. 11 via anexample Dual Port Router 804. The DRE inputs control the Dual PortRouter to allow the data register to be accessed by the TSM as describedin FIG. 5 or by the CMD circuit as described in FIG. 10. The dataregister is clocked by the free running TCK.

The Dual Port Router 804 in this example is simply multiplexers andgating connected as shown that are controlled by the DRE input from theinstruction register. When the data register is to be controlled by theTSM, the DRE input routes the Capture, Shift and Update state outputsfrom the TSM through the Dual Port Router to the Capture, Shift andUpdate inputs of the data register. The Capture state signal is assertedwhen the TSM is in the CaptureDR state, the Shift state signal isasserted when the TSM is in the ShiftDR state and the Update statesignal is asserted when the TSM is in the UpdateDR state. When the dataregister is to be controlled by the CMD circuit, the DRE input routesthe Capture (C) and Update (U) signals from the CMD circuit through theDual Port Router to the Capture, Shift and Update inputs of the dataregister. The Capture (C) input from the TSM sets the Capture and Shiftinputs of the data register to states that cause the data register toshift or capture data. In this example, if Capture (C) is low, theCapture and Shift inputs to the data register are set low and highrespectively, causing the data register to shift data from TDI to TDOand if Capture (C) is high, the Capture and Shift inputs to the dataregister are set high and low respectively, causing the data register tocapture data. The first port of this example Dual Port Router is definedas being the Capture, Shift and Update state outputs from the TSM. Thesecond port of this example Dual Port Router is defined as being theCapture (C) and Update (U) inputs from the CMD circuit.

During access by the CMD circuit, the first FF inputs the CMD signalfrom TMS and outputs an Update (U) signal to the Dual Port Router whichoutputs the Update signal to cause the data register to perform anUpdate operation. The CMD signal is then shifted into the second FFwhich outputs a Capture (C) signal to the Dual Port Router which outputsCapture and Shift signals to cause the data register to perform aCapture operation. The Capture, Shift and Update data register operationof this example occurs on the rising edge of the free running TCK. Ifdesired the Update circuitry in the data register could be designed tooperate in the response to the Update signal on the falling edge of TCKby simple inverting the TCK input to the Update circuitry. The Updateand Capture operation sequence is repeated each time a CMD signal isinput to the CMD circuit.

FIG. 13 illustrates the asynchronous CS data register 602 of FIG. 6connected to the TSM 102 and a CMD circuit 802 via a Dual Port Router804. The Dual Port Router of this example consists of a multiplexer andgates connected as shown. The DRE inputs control the multiplexer andgates of the Dual Port Router to allow the data register to be accessedby the TSM as described in FIG. 6 or by the CMD circuit as described inFIG. 10. The first port of the Dual Port Router includes the ClockDR andShiftDR outputs from the TSM. The second port of the Dual Port Routerincludes the Capture (C) output from the CMD circuit and the ClockDRoutput from the TSM. The CMD circuit in this example is simply a FF thatinputs the CMD signal from TMS on the falling edge of TCK. During accessby the CMD circuit, the FF inputs the CMD signal from TMS and outputs aCapture (C) signal to the Dual Port Router which outputs a logic stateon the ShiftDR signal, via the multiplexer and gate, to cause the dataregister to perform a Capture operation on the rising edge of ClockDRfrom the TSM. The ClockDR signal is active since the TSM is in theShiftDR state. Following the Capture operation, the ShiftDR signalreturns to it previous state to resume the Shift operation on the nextrising edge of ClockDR. The Capture operation is repeated each time aCMD signal is input to the CMD circuit.

FIG. 14 illustrates the synchronous CS data register 702 of FIG. 7connected to the TSM 102 and the CMD circuit 802 of FIG. 12 via a DualPort Router. The Dual Port Router of this example consists ofmultiplexers and gates connected as shown. The DRE inputs control themultiplexers and gates of the Dual Port Router to allow the dataregister to be accessed by the TSM as described in FIG. 7 or by the CMDcircuit as described in FIG. 10. The first port of the Dual Port Routerincludes the Capture and Shift state outputs from the TSM. The secondport of the Dual Port Router includes the Capture (C) output from theCMD circuit. The data register is clocked by the free running TCKsignal. DRE inputs control the Dual Port Router to allow the dataregister to be accessed by the TSM as described in FIG. 7 or by the CMDcircuit as described in FIG. 10. During access by the CMD circuit, theFF inputs the CMD signal from TMS and outputs a Capture (C) signal tothe Dual Port Router which outputs which set the Capture and Shiftinputs to the data register to states that cause the data register toperform a Capture operation on the rising edge of TCK. Following theCapture operation, the Capture and Shift signals return to theirprevious state to resume the Shift operation on the next rising edge ofTCK. The Capture operation is repeated each time a CMD signal is inputto the CMD circuit.

FIG. 15 illustrates the asynchronous CS data register 602 of FIG. 6connected to the TSM 102 and a CMD circuit 802 via the Dual Port Router804 of FIG. 13. As described in FIG. 13, DRE inputs control the DualPort Router to allow the data register to be accessed by the TSM asdescribed in FIG. 6 or by the CMD circuit. In this example, the CMDcircuit is designed to control the data register to perform back to backCapture operations. The CMD circuit of this example consists of firstand second serially connected FFs. The outputs of the FFs are input to agate, such as a NOR gate. The output of the gate is input to the DualPort Router. In response to a CMD input signal from TMS the first FF ofthe CMD circuit outputs a first Capture (C) signal then the CMD signalis shifted into the second FF of the CMD circuit which outputs a secondCapture signal. The CMD circuit inputs both the first and second Capturesignals (C) to the Dual Port Router, via the gate. In response to thefirst Capture (C) signal the Dual Port Router sets the ShiftDR input tothe data register to a state to cause the data register to perform afirst Capture operation on the rising edge of ClockDR. In response tothe second Capture (C) signal the Dual Port Router maintains the capturestate on the ShiftDR input to cause the data register to perform asecond Capture operation on the next rising edge of ClockDR. Followingthe back to back Capture operations the ShiftDR input to the dataregister returns to its previous state to resume the Shift operation.

While FIGS. 8-15 illustrate various types of simple data registers beingcontrolled by either the TSM or a CMD circuit, these data registerstypically form the building blocks of more complex test architectureswithin devices. These more complex test architectures can also becontrolled by the TSM or CMD circuit, as described in FIGS. 16-17 below.

Also while FIGS. 8-15 show the CMD circuit to be either a single flipflop or a serial arrangement of two flip flops, the CMD circuit may bedesigned in many different ways, including a CMD circuit designed as astate machine.

FIG. 16 illustrates a simple example of a known type of single input andsingle output test compression architecture 1602 within a device. Thearchitecture consists of a Decompressor (D) circuit, parallel CS typeData Registers (DR), and a Compactor (C) circuit. The Decompressor iscontrolled by the DRC outputs of the Dual Port Router to inputcompressed stimulus data from TDI, decompress the stimulus data andoutput the decompressed stimulus data to the CS data registers. TheCompactor is controlled by the DRC outputs of the Dual Port Router toinput response data from the CS data registers, compact the responsedata and output the compacted response data on the TDO output. The CSdata registers are controlled by the DRC outputs of the Dual Port Routerto perform capture and shift operations. DRE inputs control the DualPort Router to allow the test compression architecture to be controlledby the DRC outputs of the TSM like described in FIG. 6 or 7 or by theDRC outputs of the CMD circuit as described in FIGS. 13 and 14.

FIG. 17 illustrates a simple example of a known type of multiple inputand multiple output test compression architecture 1702 within a device.The structure and operation of the architecture is the same as describedin FIG. 16 with the exception that multiple TDI inputs are used to inputthe compressed stimulus data and multiple TDO output are used to outputthe compacted response data. The multiple input multiple output testcompression architecture can be selectively controlled by either the TSMor the CMD circuit as described in FIG. 16.

FIG. 18 illustrates a simple example of an IEEE 1500 core wrapperarchitecture 1802 within a device that is connected to the DRC outputsof a Dual Port Router. The architecture consists of a Wrapper BoundaryRegister (WBR) and parallel CS type Data Registers (DR). While not shownthe architecture also includes an instruction register to control itstest operation modes.

The wrapper boundary register is primarily used to provide interconnecttesting between multiple core wrapper architectures in a device. It canbe implemented as either a CSU or CS type data register. Duringinterconnect testing, the wrapper boundary register is controlled by theDRC outputs of the Dual Port Router to shift data through the wrapperboundary register via the wrapper serial input (WSI) and wrapper serialoutput (WSO) and then perform an update and a capture operation. In thisexample the WSI is shown connected to TDI and the WSO is shown connectedto TDO. If the TSM is selected by the DRE inputs to the Dual Port Routerto control the interconnect test, the TSM will cycle through dataregister scanning states to output the DRC signals to control thewrapper boundary register. If the CMD circuit is selected by the DREinputs to the Dual Port Router to control the interconnect test, the TSMwill transition to and remain in the ShiftDR state while the CMD circuitoutputs the DRC signals to control the wrapper boundary register.

The parallel CS data registers are used to perform parallel scan testingof the core's logic. During parallel scan testing the CS data registersare controlled by the DRC outputs of the Dual Port Router to shift datathrough the CS data registers via the wrapper parallel inputs (WPI) andwrapper parallel outputs (WPO) and then perform a capture operation. Ifthe TSM is selected by the DRE inputs to the Dual Port Router to controlthe parallel scan test, the TSM will cycle through data registerscanning states to output DRC signals to control the parallel CS dataregisters. If the CMD circuit is selected by the DRE inputs to the DualPort Router to control the interconnect test, the TSM will transition toand remain in the ShiftDR state while the CMD circuit outputs DRCsignals to control the parallel CS data registers.

Controlling the device test architectures shown in FIGS. 16-18conventionally with the TSM will bring into play the problematic deadstates during the scan operations. Controlling the test architectureswith the CMD circuit advantageously eliminates these dead states duringthe scan operations.

While the examples of FIGS. 16-18 have shown how the CMD circuit andDual Port Router may be used to improve scan or scan compression testingof a device, the CMD circuit may also be used to improve scan access toother types of embedded circuits in a device that are interfaced to aTAP. The following describes two such embedded circuits.

FIG. 19 illustrates an arrangement 1900 consisting of an addressable R/Wcircuit 1902 connected to a R/W data register 1904 that is selectivelycontrolled by the TSM 102 or by a CMD circuit 802 via a Dual Port Router804. The R/W circuit could be a memory, a test, a debug or a tracecircuit. The R/W circuit receives address input and R/W control inputfrom the data register to allow data to be written to and/or read froman addressed location in the R/W circuit via the data bus connectionbetween the R/W circuit and the data register.

When TSM controlled access to the R/W circuit is desired, the DRE inputscontrol the Dual Port Router to connect the DRC outputs from the TSM tothe DRC inputs of the data register. Once connected, the TSM transitionsto the ShiftDR state to shift address, data and R/W control bits to andfrom the data register. If the R/W control bits are set for a writeoperation, the data in the data register is written to the addressedlocation of the R/W circuit when the TSM transitions to the UpdateDRstate. If the R/W control bits are set for a read, the data in theaddressed location of the R/W circuit is loaded into the data registerwhen the TSM transitions to the CaptureDR state. If the R/W control bitsare set for a read and write operation a read from addressed location ofthe R/W circuit occurs in the CaptureDR state and a write to theaddressed location of the R/W circuit occurs in the UpdateDR state.

When CMD circuit controlled access to the R/W circuit is desired, theDRE inputs control the Dual Port Router to connect the DRC outputs ofthe CMD circuit to the DRC inputs of the data register. Once connected,the TSM transitions to and remains in the ShiftDR state to shiftaddress, data and R/W control bits to and from the data register. Atappropriate times during the shift operation, CMD inputs are input tothe CMD circuit to cause the CMD circuit to output DRC signals to theDual Port Router. If the R/W control bits are set for a write operation,the data in the data register is written to the addressed location inresponse to the CMD circuit's DRC signals. If the R/W control bits areset for a read operation, the data in the addressed location is loadedinto the data register in response to the CMD circuit's DRC signals. Ifthe R/W control bits are set for a read and write operation, the readand write occurs in response to the CMD circuit's DRC signals.

The advantage of the CMD circuit controlled R/W operations is that theTSM does not have to transition out of the ShiftDR state to the performread and/or write operations. The read and/or write operations areperformed by CMD inputs while the address, data and RW control bits arecontinuously shifted to and from the data register. If the data registeris say 50 bits long, a read and/or a write operation can be commanded tooccur following every 50th shift operation.

FIG. 20 illustrates an instrumentation data register architecture 2002being developed by IEEE standard P1687 for accessing embeddedinstruments in a device. The instrumentation data register architectureconsists of segment insertion bit (SIB) elements that can be controlledby scan operations to connect or disconnect an instrument in the pathbetween TDI and TDO. The instrumentation data register architecturemimics the operation of a self-controlled variable length scan pathfirst described by Whetsel in U.S. Pat. No. 4,872,169. Theinstrumentation data register architecture is being specified to includeDRC control inputs to allow it to be connected to and controlled by theDRC outputs from a TSM. In this example, a CMD circuit and Dual PortRouter have been added to illustrate how the instrumentation dataregister may also be controlled by a CMD circuit.

When TSM controlled access to the instrumentation data register isdesired, the DRE inputs control the Dual Port Router to connect the DRCoutputs from the TSM to the DRC inputs of the data register. Onceconnected, the TSM transitions to the ShiftDR state to shift data to andfrom the instrumentation data register. If a SIB is set to connect itsassociated instrument into the data register, data can be written to theinstrument in the UpdateDR state and read from the instrument in theCaptureDR state in the same manner as described for the R/W circuit ofFIG. 19.

When CMD circuit controlled access to the instrumentation data registeris desired, the DRE inputs control the Dual Port Router to connect theDRC outputs of the CMD circuit to the DRC inputs of the data register.Once connected, the TSM transitions to the ShiftDR state to shift datato and from the data register. If a SIB is set to connect its associatedinstrument into the data register, data can be written to the instrumentand read from the instrument in response to a CMD input to the CMDcircuit in the same manner as described for the R/W circuit of FIG. 19.

The advantage of the CMD circuit controlled instrument access operationsis the same as the CMD circuit controlled R/W circuit access operations,that being the TSM does not have to transition out of the ShiftDR stateto the perform read and/or write operations since they are performed bythe CMD inputs while data continuously shifts in and out of theinstrumentation data register.

Improving Board Level Test Operations

FIG. 21 illustrates an arrangement 2102 of daisy-chained devicesconnected to a JTAG controller. The devices may be ICs on a board orembedded circuits in an IC. Each device has a Commandable TAP (CTAP),i.e. each device TAP includes the CMD circuit and Dual Port Router ofthis disclosure. In this example the device CTAPs have been loaded witha CMD controlled IEEE 1149.1 Extest boundary scan instruction to enableat-speed update and capture operations across the interconnects. As seenin the timing diagram, the Update, Capture and Shift boundary scan testoperations are performed in response to CMD inputs from TMS, aspreviously described. In this example the Update operation occurs on therising edge of TCK and the Capture operation occurs on the followingrising edge of TCK. This provides an Extest boundary scan update andcapture operation that occurs within one TCK period, versus the two andone half TCK periods of a conventional Extest boundary scan update andcapture operation.

If desired, the Update operation could be delayed, by design of the DualPort Router, to where it occurs on the falling edge of TCK and theCapture operation occurs on the following rising edge of TCK, placingonly a one half TCK period between update and capture. This timingtightening between Update and Capture operations can be applied to anytype of CSU data register.

During the at-speed boundary scan test, normal TMS signals are input onthe rising edge of TCK to maintain the CTAPs in the ShiftDR state. TheCTAPs can also be set to perform conventional Extest boundary scantesting of the interconnects using TSM state transitions. However, thetest will not be an at-speed Update and Capture test since the TSM deadstates will be introduced.

IEEE standard 1149.6 was developed to provide a boundary scan testcapable of testing AC coupled interconnects between devices. 1149.6 wasneeded because the 1149.1 Extest instruction could not adequately testall AC coupled interconnects due to the 2 and a half TCK delay betweenthe Update and Capture operation. Since the CMD controlled Extestoperation described above can update and capture data across theinterconnects within one or even one half a TCK period, it enablestesting of AC coupled interconnects that are resistant to testing usingthe normal 1149.1 Extest instruction.

FIG. 22 illustrates an arrangement 2202 of daisy-chained devicesconnected to a JTAG controller. The devices may be ICs on a board orembedded circuits in an IC. In this example, it is desired to access aCS or CSU type circuit residing in the middle device. The CS or CSUcircuit may be any of the types previously described that communicatedata using only TDI and TDO. To setup the access to the middle device,the leading and trailing devices are loaded with an IEEE 1149.1instruction, i.e. an 1149.1 Bypass, Clamp or HighZ instruction, thatselects their Bypass (BYP) register and the middle device is loaded withan instruction to select a desired CS or CSU type circuit for access.

If the access to the CS or CSU circuit of the middle device is to beperformed using normal JTAG scan operations, the instruction loaded intothe middle device will connect the device's TSM to the CS or CSUcircuit. Access to the middle device circuit is performed by the JTAGcontroller executing conventional data register Capture, Shift andUpdate operations. During a Capture operation the Bypass registerscompliantly load logic zeros and the middle device circuit loads data tobe output to the controller during the next Shift operation. Following aShift operation, an Update operation is performed to update data thathas been shifted into the middle circuit, assuming it's a CSU typecircuit. During each data register scan operation the JTAG controllermust shift data through the Bypass registers of the leading devices,through the middle device circuit and through the Bypass registers ofthe trailing devices. If there are 50 leading devices, 50 trailingdevices and the middle device circuit scan length is 50 bits, each dataregister scan cycle will be 150 bits long. If a large number of scancycles are required to access the middle device circuit, a considerableamount time may be wasted by having to repeatedly shift data through theleading and trailing device Bypass registers.

If the access the CS or CSU circuit of the middle device is to beperformed using the CMD circuit, meaning the TAP of the middle circuitwill be augmented with the CMD circuit and Dual Port Router of thisdisclosure, the instruction loaded into the middle device will connectthe device's CMD circuit to the CS or CSU circuit. Access to the middledevice circuit is performed by the JTAG controller placing all devicesin the ShiftDR state to continuously shift data though the devices fromTDI to TDO. At appropriate times during the shifting the JTAG controllerinputs CMD signals to the CMD circuit of the middle device, via the TMSsignal. In response to the CMD inputs, CS circuits will perform aCapture operation and then resume shifting data, as seen in the CSOPtiming of FIG. 22. In response to the CMD inputs, CSU circuits willperform an Update operation followed by a Capture operation and thenresume shifting data, as seen in the CSUOP timing of FIG. 22. Since theBypass registers of the leading and trailing devices do not respond tothe CMD inputs, they simply operate as pipeline bits shifting data fromthe JTAG controller to the middle device and from the middle device backto the JTAG controller.

During access to the middle device, the only time wasted having totraverse the Bypass registers is once at the beginning of the accesswhen data from the JTAG controller fills the leading device Bypassregisters and once at the end of the access when data from the middledevice is emptied to the JTAG controller from the trailing device Bypassregisters. Reusing the example 50 leading devices, 50 trailing devices,and a 50 bit middle device circuit length, the access to the middledevice is only lengthened by a one time 50 bit shift at the beginning ofthe access and a one time 50 bit shift at the ending of the access.

Adapting JTAG Controllers for CMD Outputs

The approach of this disclosure to input CMDs using the TMS signalrequires modification of legacy JTAG controllers. There are two basictypes of JTAG controllers, software controlled JTAG controllers andhardware controlled JTAG controllers. Software controlled JTAGcontrollers simply use a computers parallel port to operate the TMS,TCK, TDI and TDO signals using software. Hardware controlled JTAGcontrollers use a JTAG interface circuit to control the TMS, TCK, TDIand TDO signals. Adapting software controlled JTAG controllers toprovide the CMD signals on TMS is achieved by simply modifying thesoftware that controls the parallel port. Adapting hardware controlledJTAG controllers to provide the CMD signals on TMS is more difficultsince it requires modifying the hardware. The following describes asimple way to modify hardware controlled JTAG controllers to provide theCMD signals on TMS.

FIG. 23 illustrates an example hardware controlled JTAG controller 2302which consists of a computer 2306 and a JTAG interface circuit 2304. TheJTAG interface circuit has a TMS control circuit for outputting TMSsignals, a TCK control circuit for outputting TCK signals, a TDI memoryfor outputting TDI signals and a TDO memory for inputting TDO signals.The computer performs reads and writes to the JTAG interface circuit tocause the JTAG interface circuit to operate the TMS, TCK, TDI and TDOsignals.

FIG. 24 illustrates an example arrangement 2402 showing how the JTAGcontroller of FIG. 23 could be augmented with a CMD circuit 2404 and amultiplexer 2406 to selectively allow it to provide or not provide theCMD signals on TMS. The CMD circuit has a computer interface, a ShiftDRstate input, a TCK input, an Enable output and a CMD output. The TCKinput times the CMD circuit and the ShiftDR state input enables theoperation of the CMD circuit. The multiplexer has an enable inputconnected to the Enable output, a data input connected to the CMDoutput, a data input connected to the TMS output, a Select inputconnected to the TCK output and an output connected to the TMS output.When the JTAG controller arrangement 2402 is set to not provide the CMDsignal on TMS, the Enable signal will be set to cause the multiplexer toonly output the TMS signal, duplicating the operation of the legacy JTAGcontroller of FIG. 23. When the JTAG controller arrangement 2402 is setto provide the CMD signals on TMS, the Enable signal will be set tocause the multiplexer to alternate between outputting the TMS signal andthe CMD signal in response to the Select input from the TCK signal.

FIG. 25 illustrates an example implementation of the CMD circuit 2404 ofFIG. 24 consisting of a Register 2502 and Counter 2504. The Registercontains a Shift Count bit field and the Enable bit. When the JTAGcontroller arrangement of FIG. 24 is to perform normal JTAG operations,the computer sets the Enable bit to cause the multiplexer to only outputTMS signals. When the JTAG controller arrangement 2402 is to perform CMDoperations, the computer writes a Shift Count to the Register, sets theEnable bit to cause the multiplexer to alternately output TMS and CMDsignals in response to the Select signal and loads the Shift Count intothe Counter. The Shift Count is set equal to the bit length of the dataregister being accessed. During CMD'ed operations, the ShiftDR stateinput is set to enable the Counter to count once per rising edge TCKshift operation. When the Shift Count expires, the Counter outputs aCount Complete (CC) signal which sets the CMD signal high. The CMDsignal is output on TMS, via the multiplexer, to trigger a CMD'edoperation in a target device. As seen in the timing diagram of FIG. 25,NOP signals are output on TMS until the CMD signal occurs. The CC signalalso Loads (LD) the Shift Count into the Counter for the next CMD'edshift cycle. The operation repeats until the test is complete. When inthe CMD signal output mode, the JTAG controller arrangement 2402 of FIG.24 provides a one half TCK setup time for the TMS signal prior to therising TCK edge and a one half TCK setup time for the CMD signal priorto the falling TCK edge.

FIG. 26 illustrates a circuit block 2602 containing one or more CSUand/or CS data register elements. Circuit block 2602 could be any typeof circuit including but not limited to a test circuit, a debug circuit,a trace circuit, an emulation circuit, read/write circuit and aninstrumentation circuit. Some examples of such circuits were describedin regard to FIGS. 16-20. The circuit block is controlled by the DRCoutputs of a Dual Port Router 804 to perform Capture and Shift orCapture, Shift and Update operations. DRE inputs control the Dual PortRouter to allow the circuit block 2602 to be controlled by the DRCoutputs of the TSM 102 or CMD circuit 2604 as previously described. TheCMD circuit 2604 of this example has additional inputs for a Capturesignal and an Update signal. In response to DRE inputs, the Capture andUpdate signals can be selected to control the DRC outputs of the CMDcircuit 2604. During device manufacturing test at wafer or packagelevel, it may be desirable to allow an external tester to directlycontrol the DRC outputs of the CMD circuit using the Capture and Updatesignals, which are made accessible on device leads during test. Allowinga tester to control the DRC outputs of the CMD circuit, via the Captureand Update signals, enables more flexible control of the CMD circuit'sDRC outputs. Also it allows the TMS input to the TSM to only have toinput the TMS signal, not the TMS and CMD signal which simplifies thetesters interface to the TAP 102. Further, only having to input the TMSsignal on the TMS input can enable the TCK to run at faster clockfrequencies since better setup and hold times can be applied on the TMSsignal. During test using the Capture and Update signals, the testerwill transition the TAP to the ShiftDR state to shift data to and fromcircuit block 2602 via the TDI and TDO signals and at appropriate timesduring the shifting operate the Capture and Update signals to effectuatetesting circuit block 2602.

FIG. 27 illustrates one example implementation of CMD circuit 2604 whichconsists of the previously described CMD circuit 804 of FIGS. 13 and 14and a multiplexer 2702. When the CMD circuit 2604 is set to allow theCMD circuit 804 to control the Capture (C) output, DRE input will setthe multiplexer to couple the Capture (C) output to the output of theCMD circuit 804 to allow the at speed Shift & Capture operation asdescribed in FIGS. 13 and 14. When the CMD circuit 2604 is set to allowthe Capture signal to control the Capture (C) output, DRE input will setthe multiplexer to couple the Capture signal to the Capture (C) outputto allow a tester to directly control the at-speed Shift & Captureoperation. CMD circuit 804 control of the Capture (C) output willadvantageously be used when the device is in a system with other devicessuch as seen in FIGS. 21 and 22. Capture signal control of the Capture(C) output will advantageously be used when the device is being testedby a tester at wafer or package level device test.

FIG. 28 illustrates another example implementation of CMD circuit 2604which consists of the previously described CMD circuit 804 of FIGS. 11and 12 and multiplexers 2702 and 2802. When the CMD circuit 2604 is setto allow the CMD circuit 804 to control the Update (U) and Capture (C)outputs, DRE input will set the multiplexer to couple the Update (U) andCapture (C) outputs to the outputs of the CMD circuit 804 to allow theat speed Update & Capture and Shift & Capture operations as described inFIGS. 11 and 12. When the CMD circuit 2604 is set to allow the Updateand Capture signals to control the Update (U) and Capture (C) outputs,DRE input will set the multiplexer to couple the Update and Capturesignals to the Update (U) and Capture (C) outputs to allow a tester todirectly control the at-speed Update & Capture and Shift & Captureoperations. CMD circuit 804 control of the Update (U) and Capture (C)outputs will advantageously be used when the device is in a system withother devices such as seen in FIGS. 21 and 22. Update and Capture signalcontrol of the Update (U) and Capture (C) outputs will advantageously beused when the device is being tested by a tester at wafer or packagelevel device test.

FIG. 29A illustrates a TAP 2902 that is identical to TAP 800 of FIG. 8with the exception that the CMD input to CMD circuit 802 comes from anoutput 2904 of the TSM 102 instead of from the TMS input. The CMD output2904 from the TSM occurs when the TSM is in the Exit1DR state. This isachieved by using a state decode gate to detect when the TSM is in theExit1DR state as shown in FIG. 29B.

FIG. 30 illustrates the timing diagram of the TSM transitioning throughthe Exit1DR state (shaded) to output the CMD signal to the CMD circuitof FIG. 29A. As seen, the CMD circuit registers the CMD signal (shaded)from the falling edge of TCK to the next falling edge of TCK asdescribed with the CMD circuit of FIG. 8. The CMD operation occurs onthe rising edge 3008 of TCK between the two falling edges of TCK. If theCMD operation performs a Capture and Shift operation (CSOP) 3002 usingthe example CMD circuit 802 of FIGS. 13 and 14, the Capture occurs onthe rising edge of TCK 3008. If the CMD operation performs a Capture,Shift and Update operation (CSUOP) 3004 using the example CMD circuit802 of FIG. 11 or 12, the Update operation occurs on the rising edge ofTCK 3008 and the Capture operation occurs on the next rising edge of TCK3010. If the CMD operation performs a Back to Back Capture and Shiftoperation (B2BCSOP) 3006 using the example CMD circuit 802 of FIG. 15,the first Capture operation occurs on the rising edge of TCK 3008 andthe second Capture operation occurs on the next rising edge of TCK 3010.

As seen in the timing diagram of FIG. 30, and unlike the timing diagramof FIG. 10, the TSM must transition out of the ShiftDR state to passthrough the Exit1DR state to provide the CMD signal to CMD circuit 802.For CSOPs 3002, this means that two dead states (i.e. no action states)PauseDR and Exit2DR must be traversed before resuming the ShiftDR statefollowing the Capture operation. For CSUOPs 3004, this means that onedead state Exit2DR must be traversed before resuming the ShiftDR statefollowing the Update and Capture operations. For B2BCSOPs 3006, thismeans that one dead state Exit2DR must be traversed before resuming theShiftDR state following the first and second Capture operations. Whiledead states are introduced using the Exit1DR state to detect the CMDsignal, the dead states occur after the desired at-speed Shift andCapture operations (CSOP) 3002, at-speed Update and Capture operations(CSUOP) 3004 and at speed Back to Back Capture operations (B2BCSOP)3006.

It is known that when the TSM 102 transitions from the ShiftDR state, itceases or gates off the outputting of clock signals on its ClockDRoutput. As seen in the timing diagram of FIG. 30, the CSOP operation3002 requires a clock in the Exit1DR state for the Capture operation,the CSUOP operation 3004 requires a clock in the Exit1DR and PauseDRstates for the Update and Capture operations and the B2BCSOP operation3006 requires a clock in the Exit1DR and PauseDR states for the Back toBack Capture operations. The following description of FIGS. 31 and 32will illustrate an example of how to provide these clocks on ClockDRduring these states.

FIG. 31 illustrates an asynchronous register 3102, Dual Port Router 804,CMD circuit 802 and TSM 102. Asynchronous data register 3102 could be anasynchronous CSU data register 402 or an asynchronous CS data register602. If it is an asynchronous CSU data register 402 the CMD circuit 802will operate as described in FIG. 11 to provide the ClockDR, ShiftDR andUpdate signals to the data register via the Dual Port Router 804. If itis an asynchronous CS data register 602 the CMD circuit 802 will operateas described in either FIG. 13 or FIG. 15 to provide the ClockDR andShiftDR signals to the data register via the Dual Port Router 804. Theonly difference between the arrangement of FIG. 31 and other previouslydescribed arrangements using CMD circuits 802 is that the CMD signal tothe CMD circuit of FIG. 31 comes from the TSM instead of from the TMSsignal. The TSM includes the gating circuit 2904 of FIG. 29B to providethe CMD signal during the Exit1DR state and further ClockDR gatingcircuitry 3102 to provide clock signals on ClockDR as described abovefor the CSOP, CSUOP and B2BCSOP operations.

FIG. 32 illustrates an example of the TSM's ClockDR gating circuitry3102 which includes gating circuits 3204-3208 and a multiplexer 3202,all connected as shown. Each gating circuit 3204-3208 inputs the TCKsignal and four state signals indicative of the TSM state. Gatingcircuitry 3204 passes TCK to the multiplexer when the TSM is in theCaptureDR or ShiftDR state. Gating circuitry 3206 passes TCK to themultiplexer when the TSM is in the CaptureDR, ShiftDR or Exit1DR state.Gating circuitry 3208 passes TCK to the multiplexer when the TSM is inthe CaptureDR, ShiftDR, Exit1DR or PauseDR state. The multiplexerreceives DRE input from the instruction register to select which gatingcircuit output to pass on to the ClockDR output.

When the TSM is controlling the DRC signals to the data register 3102,the output of gating circuit 3204 will be multiplexed to the ClockDRoutput of multiplexer 3202 to allow conventional IEEE 1149.1 TSMcontrolled Capture and Shift or Capture, Shift and Update operations.When the CMD circuit is controlling the DRC signals to the data register3102 during CSOP operations 3002 of FIG. 30, the output of gatingcircuitry 3206 will be multiplexed to the ClockDR output of multiplexer3202 to provide the required additional Capture clock on ClockDR duringthe Exit1DR state. When the CMD circuit is controlling the DRC signalsto the data register 3102 during CSUOP operations 3004 of FIG. 30, theoutput of gating circuitry 3208 will be multiplexed to the ClockDRoutput of multiplexer 3202 to provide the required additional Updateclock on ClockDR during the Exit1DR state and the required Capture clockon ClockDR during the PauseDR state. When the CMD circuit is controllingthe DRC signals to the data register 3102 during B2BCSOP operations 3006of FIG. 30, the output of gating circuitry 3208 will be multiplexed tothe ClockDR output of multiplexer 3202 to provide the requiredadditional first Capture clock on ClockDR during the Exit1DR state andthe required additional second Capture clock on ClockDR during thePauseDR state.

FIG. 33 illustrates an arrangement including a circuit block 2602, DualPort Router 804, TSM 102 and CMD circuit 2604. FIG. 33 is identical toFIG. 26 with the exception that the TSM has been modified, as previouslydescribed in FIG. 31 to output CMD signals to the CMD circuit 2604 viagating circuitry 2904 during the Exit1DR state and clock signals to theDual Port Router via gating circuitry 3104 during other selected TSMstates. As described in regard to FIGS. 26, 27 and 28, the DRC inputs tothe circuit block 2602 from the Dual Port Router may be controlled byeither the CMD circuit or from a tester connected to externallyaccessible Capture and Update signals.

FIG. 34A illustrates a TAP 3402 that is similar to TAP 2902 of FIG. 29Ain that it includes Data Registers 106, Dual Port Router 804,Instruction Register 104, multiplexing circuitry 110 and TSM 102. Itdiffers from TAP 2902 in that TAP 3402 uses a Programmable Switch (PSW)circuit 3406 instead of the CMD circuit 802. The TSM 102 has beenaugmented with TSM state detecting circuitry 3404. The TSM statedetecting circuitry is implemented to detect the Exit1DR and PauseDRstates as shown in the example of FIG. 34B. The detected Exit1DR (EDR)and detected PauseDR (PDR) TSM state signals are input to the PSWcircuit along with DRE input from the instruction register. The PSWcircuit outputs DRC control to the Dual Port Router 804 to controlCapture and Shift, Capture, Shift and Update or Back to Back Capture andShift operations on a selected one or more data registers. The DRE inputto the PSW circuit programs it to couple the EDR and PDR signals toappropriate DRC signals as needed to perform a CSOP, CSUOP or B2BCSOPoperations on a data register.

FIG. 35 illustrates the timing diagram of the TSM transitioning throughstates to perform CSOP operations 3502, CSUOP operations 3504 andB2BCSOP operations 3506 using the state detecting circuitry 3404 and thePSW circuit 3406. During CSOP operations 3502, a detected Exit1DR statepasses through the PSW to cause the Dual Port Router to output DRCcontrol to perform a Capture operation on a selected data register.During CSUOP operations 3504, a detected Exit1DR state passes throughthe PSW to cause the Dual Port Router to output DRC control to performan Update operation on a selected data register and a detected PauseDRstate passes through the PSW to cause the Dual Port Router to output DRCcontrol to perform a Capture operation on the selected data register.During B2BCSOP 3506 operations, a detected Exit1DR state passes throughthe PSW to cause the Dual Port Router to output DRC control to perform afirst Capture operation on a selected data register and a detectedPauseDR state passes through the PSW to cause the Dual Port Router tooutput DRC control to perform a second Capture operation on the selecteddata register.

Like the timing diagram of FIG. 30, the timing diagram of FIG. 35includes dead states. As seen, two dead states occur during CSOPoperations 3502, one dead state occurs during CSUOP operations 3504 andone dead state occurs during B2BCSOP operations 3506. The dead statesare not troublesome since they occur after the desired at-speed Captureoperation during CSOP cycles 3502, after the desired at-speed Update andCapture operations during CSUOP cycles 3504 and after the desiredat-speed Back to Back Capture operations during B2BCSOP cycles 3506.

FIG. 36 illustrates an asynchronous register 3602, Dual Port Router 804,TSM 102 and PSW circuit 3406 all connected as shown. Asynchronous dataregister 3602 could be an asynchronous CSU data register 402 or anasynchronous CS data register 602.

If data register 3602 is an asynchronous CSU data register 402, the PSW3406 will be programmed by DRE input to couple the Exit1DR signal fromthe detecting circuit 3404 to the Update (U) signal output of the PSWand the PauseDR signal output from the detecting circuit 3404 to theCapture (C) output of the PSW. When the TSM transitions through thedetectable Exit1DR state, the Update (U) output of the PSW is assertedand is applied, via the Dual Port Router, to the UpdateDR input of theCSU data register to perform the Update operation. When the TSMtransitions through the detectable PauseDR state, the Capture (C) outputof the PSW is asserted and is applied, via the Dual Port Router, to theShiftDR input of the CSU data register to perform the Capture operation.

If data register 3602 is an asynchronous CS data register 602, and aCSOP operation is to be performed on the register, the PSW 3406 will beprogrammed by DRE input to couple the Exit1DR signal from the detectingcircuit 3404 to the Capture (C) signal output of the PSW. When the TSMtransitions through the detectable Exit1DR state, the Capture (C) outputof the PSW is asserted and is applied, via the Dual Port Router, to theShiftDR input to the CS data register to perform a Capture operation.

If data register 3602 is an asynchronous CS data register 602, and aB2BCSOP operation is to be performed on the register, the PSW 3406 willbe programmed by DRE input to couple the Exit1DR signal from thedetecting circuit 3404 to the Capture (C) signal output of the PSW andthe PauseDR signal from the detecting circuit 3404 to the Capture (C)signal output of the PSW. When the TSM transitions through thedetectable Exit1DR state, the Capture (C) output of the PSW is assertedand is applied, via the Dual Port Router, to the ShiftDR input to the CSdata register to perform the first Capture operation. When the TSMtransitions through the detectable PauseDR state, the Capture (C) outputof the PSW is again asserted and is applied, via the Dual Port Router,to the ShiftDR input to the CS data register to perform the secondCapture operation.

As seen in FIG. 36, the TSM is augmented with the previously describedClockDR gating circuitry 3104 to provide clock signals on ClockDR duringrequired TSM states, as described in FIG. 32, to perform the abovedescribed PSW controlled CSOP, CSUOP and B2BCSOP operations. The PSWcircuit 3406 can be designed in many ways, including ways that usegating circuitry and multiplexers that are controlled by DRE input andways that use gating circuitry and crossbar switches that are controlledby DRE input.

FIG. 37 illustrates an arrangement including a circuit block 2602, DualPort Router 804, TSM 102 and a new PSW circuit 3702 all connected asshown. As shown in FIG. 38, the new PSW circuit 3702 includes thepreviously described PSW circuit 3406 and two multiplexers 3802 and3804. The PSW circuit 3406 inputs Exit1DR and PauseDR signals from thepreviously described detection circuitry 3404 of TSM 102 and inputs DREinput from the instruction register. The PSW circuit 3406 outputs asignal to multiplexer 3802 and a signal to multiplexer 3804. Multiplexer3802 inputs the signal from PSW 3406, a Capture signal, a DRE controlinput signal and outputs a Capture (C) signal. Multiplexer 3804 inputthe signal from PSW 3406, an Update signal, a DRE control input signaland outputs an Update (U) signal. The new PSW 3702 can operate in twomodes as determined by DRE input. The first mode is identical to thatdescribed in FIGS. 34A and 36 where the PSW 3406 responds to detectedExit1DR and PauseDR state signals to control the Capture (C) and Update(U) outputs of the new PSW 3702 via the multiplexers 3802 and 3804. Thesecond mode allows the Capture (C) and Update (U) outputs of the new PSW3702 to be controlled by the Capture and Update signals to multiplexers3802 and 3804. As mentioned previously in FIGS. 26 and 33, the Captureand Update signals can be controlled directly by an tester during waferand package device manufacturing test while the TAP 102 is in theShiftDR state to more efficiently control CSOP, CSUOP and B2BCSOP testoperations.

FIG. 39 illustrates a TAP 3902 that is similar to TAP 3402 of FIG. 34Ain that it includes Data Registers 106, Dual Port Router 804,Instruction Register 104, multiplexing circuitry 110 and TSM 102. TAP3902 differs from TAP 3402 in that it does not include a PSW circuit3406. As seen, the TSM's Exit1DR (EDR) and PauseDR (PDR) state detectionsignals from state the detection circuit 3404 are coupled directly tothe DRC inputs of the Dual Port Router. The Dual Port Router 804 isdesigned to respond to DRE input to couple the EDR and PDR signals to aselected data register to allow the data register to perform a CSOP,CSUOP or B2BCSP operations, as described in FIG. 35, in response to thesignals.

In a first example, if Data Register 1 is a CS Data Register and a CSOPoperation 3502 as shown in FIG. 35 is to be performed, the DREinstruction inputs will control the Dual Port Router 804 to couple theEDR signal to the DRC 3904 inputs to Data Register 1 to control when theCapture operation occurs. If the CS Data Register is an asynchronous 602type register, this means the EDR signal would be coupled to the ShiftDRinput of the register, via the DRC output 3904 of the Dual Port Router804.

In a second example, if Data Register N is a CSU Data Register and aCSUOP operation 3504 as shown in FIG. 35 is to be performed, the DREinstruction inputs will control the Dual Port Router to couple the EDRand PDR signals to the DRC 3906 inputs to Data Register N to controlwhen the Update and Capture operations occur. If the CSU Data Registeris an asynchronous 402 type register, this means the EDR signal would becoupled to the UpdateDR input of the register and the PDR signal wouldbe coupled to the ShiftDR input of the register, via the DRC output 3906of the Dual Port Router 804.

FIG. 40 illustrates a TAP 4002 that is similar to TAP 3902 of FIG. 39 inthat it includes Data Registers 106, Dual Port Router 804, InstructionRegister 104, multiplexing circuitry 110 and TSM 102. TAP 4002 differsfrom TAP 3902 in that it inserts a multiplexer 4008 in the EDR and PDRsignal path between the TSM and Dual Port Router. The multiplexer hasinputs for an externally accessible Capture and Update signal. Themultiplexer is controlled by DRE input to allow the DRC input to theDual Port Router to be controlled by the EDR and PDR TSM signals or theexternally accessible Capture and Update signals. When the EDR and PDRsignals are selected to control the DRC inputs to the Dual Port Router,the TAP 4002 operates as described in FIG. 39. When the Capture andUpdate signals are selected to control the DRC inputs to the Dual PortRouter, the TAP 402 operates as described previously in FIGS. 26, 33 and37.

FIG. 41 illustrates an arrangement including a circuit block 2602, DualPort Router 804, TSM 102 and multiplexer 4008 all connected as shown.Multiplexer 4008 inputs the Exit1DR (EDR) and PauseDR (PDR) signals fromthe TSM, the Capture and Update signals and outputs DRC control to theDual Port Router as described in FIG. 40. PSW 3406, a Capture signal, aDRE control input signal and outputs a Capture (C) signal. Themultiplexer 4008 can operate in two modes as determined by DRE input.The first mode allows the Exit1DR and PauseDR signals to control the DRCinput to the Dual Port Router. The second mode allows the Capture andUpdate signals to control the DRC inputs to the Dual Port Router. Asmentioned previously in FIGS. 26 and 33, the Capture and Update signalscan be controlled directly by a tester during wafer and package devicemanufacturing test while the TAP 102 is in the ShiftDR state to moreefficiently control CSOP, CSUOP and B2BCSOP test operations to circuitblock 2602.

The value of the Dual Port Router is that it allows a target circuit tobe controlled conventionally by the TSM or by the new methods describedin this disclosure. For example, in FIG. 21 the devices in thedaisy-chain arrangement can be selectively controlled by the TSM duringstandard IEEE 1149.1 Extest instruction operations or they can becontrolled by the CMD circuit during the new at-speed Extest instructionoperations of this disclosure. According to this disclosure, anystandard or non-standard IEEE 1149.1 instruction can have two operationmodes. A first operation mode that is controlled conventionally by theTSM via the Dual Port Router and a second operation mode that iscontrolled according to the teachings of disclosure via the Dual PortRouter.

It should be understood that while a Dual Port Router is shown in theembodiments of the disclosure, it is not a required feature of thedisclosure. Indeed, if conventional TSM access to a data register 106 orother circuit 2602 is not required, the Dual Port Router may be replacedby another Router capable of receiving DRE input to couple the DRCoutputs from a CMD circuit, a PSW circuit, an Exit1DR and PauseDR statedetection circuit or from externally accessible Capture and Updatesignals to the DRC inputs of a data register 106 or a circuit 2602.

The device circuits 106 and 2602 include but or not limited to; devicetest circuits, device debug circuits, device programming circuits,device instrumentation circuits, device read/write circuits, devicetrace circuits and device emulation circuits.

Although the disclosure has been described in detail, it should beunderstood that various changes, substitutions and alterations may bemade without departing from the spirit and scope of the disclosure asdefined by the appended claims.

What is claimed is:
 1. An integrated circuit comprising: A. a test clocklead and a test mode select lead; B. a state machine having a test clockinput coupled to the test clock lead, a test mode select input coupledto the test mode select lead, and data register control outputs; C.command flip flop circuitry having a clock input coupled to the testclock lead, an input coupled to the test mode select lead, and a commandflip flop circuitry output; D. first data register circuitry havingfirst data register control inputs; E. second data register circuitryhaving second data register control inputs separate from the first dataregister control inputs; and F. dual port router circuitry having statemachine inputs connected to the data register control outputs, anotherinput connected to the command flip flop circuitry output, a dataregister enable input, first data register control outputs coupled withthe first data register control inputs, and second data register controloutputs coupled with the second data register control inputs.
 2. Theintegrated circuit of claim 1 including a test data in lead and aninstruction register having an input coupled to the test data in lead anenable output connected to the data register enable input.
 3. Theintegrated circuit of claim 1 in which the first and second dataregisters include a test data input and including a test data in leadcoupled to the a test data input of the first and second data registers.4. The integrated circuit of claim 1 in which the state machine hasstates of Test Logic Reset, Run Test/Idle, SelectDR, and SelectIR.